McCoy: What’s the matter, Spock? 

Spock: There’s something disquieting about these creatures. 

McCoy: Don’t tell me you’ve got a feeling. 

Spock: Don’t be insulting, Doctor. They remind me of the lilies of the field. They toil not, neither do they spin. But they seem to eat a great deal. I see no practical use for them. 

McCoy: Does everything have to have a practical use for you? They’re nice, soft, and furry, and they make a pleasant sound. 

Spock: So would an ermine violin, but I see no advantage in having one. 

McCoy: It’s a human characteristic to love little animals, especially if they’re attractive in some way. 

Spock: Doctor, I am well aware of human characteristics. I am frequently inundated by them, but I’ve trained myself to put up with practically anything. 

McCoy: Spock, I don’t know too much about these little tribbles yet, but there’s one thing that I have discovered. 

Spock: What is that, Doctor? 

McCoy: I like them… better than I like you. 

Spock: Doctor? 

McCoy: Yes? 

Spock: They do have one redeeming characteristic. 

McCoy: What’s that? 

Spock: They do not talk too much. If you’ll excuse me, sir.

Star Trek — Season 2: Episode 13 — “The Trouble with Tribbles”